Reduce how often LayoutSVGShape::updateShapeFromElement is called

Source/core/layout/svg/LayoutSVGEllipse.cpp

Index: Source/core/layout/svg/LayoutSVGEllipse.cpp
diff --git a/Source/core/layout/svg/LayoutSVGEllipse.cpp b/Source/core/layout/svg/LayoutSVGEllipse.cpp
index 8809a19effc56498f07bce318b1f8db40dee533e..3c14eb186daec78597a50a6efc3720218c6b85f7 100644
--- a/Source/core/layout/svg/LayoutSVGEllipse.cpp
+++ b/Source/core/layout/svg/LayoutSVGEllipse.cpp
@@ -45,38 +45,44 @@ LayoutSVGEllipse::~LayoutSVGEllipse()
 {
 }
 
+void LayoutSVGEllipse::styleDidChange(StyleDifference diff, const ComputedStyle* oldStyle)
+{
+    if (diff.needsFullLayout() && oldStyle) {
+        const SVGComputedStyle& oldSvgStyle = oldStyle->svgStyle();
+        const SVGComputedStyle& svgStyle = style()->svgStyle();
+
+        bool radiusChanged;
+        if (isSVGCircleElement(*element()))
+            radiusChanged = oldSvgStyle.r() != svgStyle.r();
+        else
+            radiusChanged = (oldSvgStyle.rx() != svgStyle.rx()) || (oldSvgStyle.ry() != svgStyle.ry());
+
+        if (oldSvgStyle.cx() != svgStyle.cx()
+            || oldSvgStyle.cy() != svgStyle.cy()
+            || radiusChanged
+            || oldSvgStyle.vectorEffect() != svgStyle.vectorEffect()
+            || hasContinuousStroke(oldSvgStyle) != hasContinuousStroke(svgStyle))
+            setNeedsShapeUpdate();
+    }
+
+    // Superclass will take care of calling clientStyleChanged.
+    LayoutSVGShape::styleDidChange(diff, oldStyle);
+}
+
 void LayoutSVGEllipse::updateShapeFromElement()
 {
-    // Before creating a new object we need to clear the cached bounding box
-    // to avoid using garbage.
-    m_fillBoundingBox = FloatRect();
-    m_strokeBoundingBox = FloatRect();
-    m_center = FloatPoint();
-    m_radii = FloatSize();
     m_usePathFallback = false;
-
     calculateRadiiAndCenter();
 
-    // Spec: "A negative value is an error. A value of zero disables rendering of the element."
-    if (m_radii.width() < 0 || m_radii.height() < 0)
+    // Fall back to LayoutSVGShape and path-based hit detection if the ellipse
+    // has a non-scaling or discontinuous stroke.
+    if (hasNonScalingStroke() || !hasContinuousStroke(style()->svgStyle())) {
+        LayoutSVGShape::updateShapeFromElement();
+        m_usePathFallback = true;
         return;
-
-    if (!m_radii.isEmpty()) {
-        // Fall back to LayoutSVGShape and path-based hit detection if the ellipse
-        // has a non-scaling or discontinuous stroke.
-        if (hasNonScalingStroke() || !hasContinuousStroke()) {
-            LayoutSVGShape::updateShapeFromElement();
-            m_usePathFallback = true;
-            return;
-        }
     }
 
     clearPath();
-
-    m_fillBoundingBox = FloatRect(m_center.x() - m_radii.width(), m_center.y() - m_radii.height(), 2 * m_radii.width(), 2 * m_radii.height());
-    m_strokeBoundingBox = m_fillBoundingBox;
-    if (style()->svgStyle().hasStroke())
-        m_strokeBoundingBox.inflate(strokeWidth() / 2);
 }
 
 void LayoutSVGEllipse::calculateRadiiAndCenter()
@@ -97,15 +103,41 @@ void LayoutSVGEllipse::calculateRadiiAndCenter()
     }
 }
 
+void LayoutSVGEllipse::updateStrokeAndFillBoundingBoxes()
+{
+    // Spec: "A negative value is an error."
+    if (m_radii.width() < 0 || m_radii.height() < 0) {
+        m_fillBoundingBox = FloatRect();
+        m_strokeBoundingBox = FloatRect();
+        return;
+    }
+
+    if (m_usePathFallback) {
+        // Spec: "A value of zero disables rendering of the element." so we can skip
+        // the path fallback and rely on the existing bounding box calculation.
+        if (!m_radii.isEmpty()) {
+            LayoutSVGShape::updateStrokeAndFillBoundingBoxes();
+            return;
+        }
+        m_usePathFallback = false;
+        clearPath();
+    }
+
+    m_fillBoundingBox = FloatRect(m_center.x() - m_radii.width(), m_center.y() - m_radii.height(), 2 * m_radii.width(), 2 * m_radii.height());
+    m_strokeBoundingBox = m_fillBoundingBox;
+    if (style()->svgStyle().hasStroke())
+        m_strokeBoundingBox.inflate(strokeWidth() / 2);
+}
+
 bool LayoutSVGEllipse::shapeDependentStrokeContains(const FloatPoint& point)
 {
     // The optimized check below for circles does not support non-scaling or
     // discontinuous strokes.
     if (m_usePathFallback
-        || !hasContinuousStroke()
+        || !hasContinuousStroke(style()->svgStyle())
         || m_radii.width() != m_radii.height()) {
-        if (!hasPath())
-            createPath();
+        if (!m_usePathFallback)
+            LayoutSVGShape::updateShapeFromElement();
         return LayoutSVGShape::shapeDependentStrokeContains(point);
     }
 
@@ -126,9 +158,8 @@ bool LayoutSVGEllipse::shapeDependentFillContains(const FloatPoint& point, const
     return xrX * xrX + yrY * yrY <= 1.0;
 }
 
-bool LayoutSVGEllipse::hasContinuousStroke() const
+bool LayoutSVGEllipse::hasContinuousStroke(const SVGComputedStyle& svgStyle) const
 {
-    const SVGComputedStyle& svgStyle = style()->svgStyle();
     return svgStyle.strokeDashArray()->isEmpty();
 }